JP6547443B2 - Fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, and a fixing apparatus of a heating system mounted on such an image forming apparatus.

  In the image forming apparatus, a toner image is formed on an image carrier based on image information, the toner image is transferred onto a recording material such as paper or an OHP sheet, and the recording material carrying the toner image is passed through a fixing device. The toner image is fixed on the recording material by heat and pressure.

As such a fixing device, as shown in FIG. 9, a configuration is known in which three regions H _{81 to} H ₈₃ are heated by two halogen heaters 801 and 802. The halogen heater 801 heats the area H ₈₂ , and the halogen heater 802 heats the area H ₈₁ and the area H ₈₃ simultaneously. Then, the halogen heater 801, one temperature sensing means 836 for detecting the temperature of the area _{H 82} is installed. On the other hand, the halogen heater 802 is provided with one temperature detection means 836 for detecting the temperature of only the region H ₈₃ . In this manner, the abnormally high temperature due to the halogen heaters 801 and 802 is detected.

  By the way, in recent years, for the purpose of energy saving, a plate-like heating member which uses a film as a fixing member and which has a plurality of heat generating parts and selectively heats an arbitrary region according to the paper width size as shown in FIG. The configuration provided is known.

  In such a fixing device, the heater member 956 is provided with a plurality of heat generating portions 956a, and one temperature detection means 936 for detecting the temperature of one of the plurality of heat generating portions is disposed. Then, the temperature detection means 936 detects the heat generation state of the heater member 956.

  By the way, in such a fixing device, even if one of the plurality of heat generating parts is broken, the other heat generating parts may generate heat. Therefore, when the heat generating portion 956a detected by the temperature detection unit 936 is damaged, there is a problem that the abnormal temperature rise by the other heat generating portion can not be detected.

  An object of the present invention is to provide a fixing device which appropriately detects an abnormal temperature rise of a heat generating portion.

In order to solve the problems described above, a fixing device according to claim 1 of the present invention is:
A belt-shaped fixing member that rotates in contact with the unfixed image;
A pressing member that forms a fixing nip portion with the belt-shaped fixing member;
A fixing device configured to fix a sheet-like recording material carrying an unfixed image on a heating member for heating the belt-like fixing member at the fixing nip portion,
The heating member includes a long base material extending in the longitudinal direction of the belt-like fixing member, and a plurality of heating elements formed on the base material.
The plurality of heating elements form at least one heating area which can be ON / OFF controlled at the same time,
In each heating area , the plurality of heating elements are electrically connected in parallel, and a plurality of temperature detection means capable of detecting the temperature of any one of the plurality of heating elements are provided. .

  According to the present invention, it is possible to provide a fixing device which appropriately detects an abnormal temperature rise of the heat generating portion.

FIG. 1 is a block diagram schematically showing an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic view of a fixing device of the image forming apparatus shown in FIG. FIG. 2 is a schematic view of a nip forming member of the image forming apparatus shown in FIG. 1; FIG. 2 is a configuration diagram showing a heating member of the image forming apparatus shown in FIG. FIG. 2 is an explanatory view for explaining a heater member of the image forming apparatus shown in FIG. 1; It is an explanatory view explaining a heater member concerning a 2nd embodiment of the present invention. It is an explanatory view explaining a heater member concerning a 3rd embodiment of the present invention. It is an explanatory view explaining a modification of a heater member concerning the present invention. It is an explanatory view explaining a conventional heater member. It is an explanatory view explaining a conventional heater member.

  FIG. 1 shows a monochrome printer as an example of an image forming apparatus according to an embodiment of the present invention, and the present invention will be described based on this. Needless to say, the present invention is similarly applicable to known color image forming apparatuses. It is a thing. In a monochrome printer, as is known, a developing device provided with a charging roller 18 as a charging unit, a mirror 20 constituting an exposure unit, and a developing roller 22a as a developing unit, around a photosensitive member 8 as an image carrier. 22, a transfer device 10, and a cleaning device 24 provided with a cleaning blade 24a are disposed. Then, between the charging roller 18 and the developing device 22, exposure light Lb is irradiated to the exposure section 26 on the photosensitive member 8 through the mirror 20 and scanned. Further, at the lower part of the printer, a sheet feeding unit 4 is disposed. A registration roller pair (alignment roller pair) 6 is provided in the middle of the sheet conveyance path to the image forming unit. At the end of the sheet conveyance path, a fixing device 12 including a fixing belt 28 (a belt-like fixing member; hereinafter simply referred to as a fixing belt), a heater member 56 and a pressure roller 30 is provided.

  The sheet feeding unit 4 separates and feeds the sheet P, which is stored in the sheet feeding tray 14 in which the sheets P as a recording material are stored in a stacked state, and the sheets P stored in the sheet feeding tray 14 one by one from the top sheet. It has a roller 16 and the like. The sheet P fed by the sheet feed roller 16 is temporarily stopped by the registration roller pair 6. Then, after the positional deviation is corrected, the front end of the toner image formed on the photoconductor 8 and the predetermined position of the front end of the sheet P in the conveyance direction coincide with each other at the timing synchronized with the rotation of the photoconductor 8. It is sent to the transfer site N by the registration roller pair 6 at timing.

  The image forming operation in this printer is performed in the same manner as in the prior art. When the photosensitive member 8 starts to rotate, the surface of the photosensitive member 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated to the exposure unit 26 based on the image information, and the image corresponds to the image to be created. An electrostatic latent image is formed. The electrostatic latent image is moved to the position opposite to the developing device 22 by the rotation of the photosensitive member 8, where the toner is supplied and visualized to form a toner image. The toner image formed on the photosensitive member 8 is transferred onto the sheet P entering the transfer site N at a predetermined timing by the transfer bias application of the transfer device 10. The sheet P carrying a toner image, which is an unfixed image, is conveyed toward the fixing device 12, fixed by the fixing device 12, and then discharged / stacked onto a sheet discharge tray outside the machine. The residual toner remaining on the photosensitive member 8 without being transferred at the transfer site N reaches the cleaning device 24 as the photosensitive member 8 rotates, and is scraped off by the cleaning blade 24 a while passing through the cleaning device 24. Be cleaned. Thereafter, the residual potential on the photosensitive member 8 is removed by known charge removing means, and is prepared for the next imaging step.

Next, the configuration of the fixing device according to the embodiment of the present invention will be described based on FIG.
The fixing device 12 includes an endless fixing belt 28 that is a flexible heat-resistant film, a pressure roller 30 that is a pressing member that abuts on the outer circumferential surface, and a heater member 56 that is a heating member. The heater member 56, together with the heat transfer member 50 for temperature equalization in the axial direction (longitudinal direction) of the fixing belt 28, serves as a nip forming member that forms the fixing nip portion SN. The heat transfer member 50, the heater member 56, and the heater holder 57 holding the same are supported by the stay (support member) 61 connected to the device side plate, and the bending of these members due to the pressure of the pressure roller 30 is prevented. A uniform nip width is obtained in the longitudinal direction. A low friction sheet may be interposed between the heat transfer member 50 and the inner circumferential surface of the fixing belt 28.

  A first thermistor 34 for detecting the surface temperature of the fixing belt 28 is provided on the downstream side of the fixing nip portion SN and on the upstream side of the heater member 56. In addition, a second thermistor 36 is provided as a temperature detection unit that detects the temperature of the heater member 56 itself. The heating control means 42 which controls the power supply 40 which supplies electric power to the heater member 56 based on the detection information of these thermistors is provided. The heating control means 42 means a microcomputer including a CPU, a ROM, a RAM, an I / O interface and the like.

  The fixing belt 28 has a nickel base having an outer diameter of 30 mm and a thickness of 10 to 70 μm, an elastic layer coated on the surface of the base, and a release layer formed on the surface. The elastic layer is formed of silicone rubber and has a thickness of 50 to 150 μm. The release layer for enhancing the durability and securing the releasability is formed of a fluorine-based resin such as PFA or PTFE, and is provided in a thickness of 5 to 50 μm. The belt substrate is not limited to nickel, and may be formed of a heat-resistant resin material such as SUS or polyimide (PI).

  The pressure roller 30 has an outer diameter of 30 mm, and has a solid iron core 30a and an elastic layer 30b formed on the surface of the core 30a. The elastic layer 30b is formed of silicone rubber and has a thickness of 5 mm. It is desirable to form a fluorine resin (PFA or PTFE) layer having a thickness of about 40 μm on the surface of the elastic layer 30 b in order to enhance releasability. As known, the pressure roller 30 is in pressure contact with the heat transfer member 50 and the heater member 56 via the fixing belt 28 by biasing means. The pressure roller 30 is rotated by transmitting a driving force from a driving source such as a motor provided in the image forming apparatus via a gear. The fixing belt 28 is rotated by the pressure roller 30.

  The heater member 56 is a plate-like heating element in which a resistance heating element 56 a as a heating element is formed on the surface of a long base 56 b extending in the axial direction (longitudinal direction) of the fixing belt 28. Is the main component of As shown in FIG. 3, for example, the resistance heating element 56a is printed and baked on a low thermal conductivity base material 56b such as glass, and an overcoat (OC) layer 56c is further formed thereon. The OC layer 56c positioned on the fixing belt 28 side is also formed of glass or the like, but is thinner than the base material 56b and easily transfers heat to the OC layer side than the base side, so the heating efficiency of the fixing belt 28 improves.

  As shown in FIG. 4, the fixing belt 28 slides on the inner peripheral surface of the heat transfer member 50 assembled and heated on the surface side of the heater member 56, so that the temperature of the belt rises. The unfixed image on the sheet conveyed to the nip portion SN can be heated and fixed. The heat transfer member 50 is formed of a high heat conductive material such as copper or aluminum. The adhesion between the heater member 56 and the heat transfer member 50 may be improved using heat conductive grease, a heat conductive sheet, or the like. By improving the adhesion, the heat conductivity to the surface side is improved more than the back surface side (the opposite side to the fixing belt) of the heater member 56 to ensure the belt heating and to improve the heat conductivity in the longitudinal direction of the heater. Can be secured.

  Further, the heater holder 57 holds the heater member 56 from the back surface side. The heater holder 57 is shaped so as not to contact the entire back surface of the heater member 56 but to remain in partial contact so that the heat conduction to the heater holder 57 is as small as possible. Low rate materials are used. A nip area is formed by contact between the pressure roller 30 and the heat transfer member 50 through the fixing belt 28. The portion where the heater holder 57 protrudes to the belt side from the contact surface is the upper and downstream of the sheet conveyance direction. Having them on the side can improve the separation of the sheet.

Next, the heater member 56 will be described.
As shown in FIG. 5, the heater member 56 extending in the axial direction of the fixing belt 28 has a plurality of resistance heating elements 56a in the longitudinal direction, that is, in the direction orthogonal to the sheet conveyance direction. Opposite electrodes are connected to the upstream and downstream sides in the sheet conveyance direction of the plurality of resistance heating elements 56a, and heat is generated uniformly in the longitudinal direction. The common wiring Wcom and the individual wirings W1 and W2 are connected to the counter electrode, and two heating areas H ₁₁ and H ₁₂ are formed. Each heating region _{H 11, H 12,} by turning ON / OFF the individual wires W1, W2, can be heated independently controlled individually.

  A first thermistor 34 for detecting the surface temperature of the fixing belt 28 and a second thermistor 36 for detecting the temperature of the heater member 56 are disposed corresponding to the respective heating areas. The temperature of each heating area is controlled by the heating control means 42 in consideration of the detection information and further the sheet passing size information, and the heating ratio of the heater member 56 is changed. By controlling the heating according to the sheet passing size information, it is possible to prevent the temperature of the non-sheet passing area from becoming excessively high, and to suppress the damage to the member and the deterioration of the image quality due to the excessive temperature rise of the non sheet passing area. In practice, the power supply may be completely stopped (turned off) at the portion corresponding to the non-sheet passing area, but if the temperature is extremely lowered excessively, it does not catch up with the rise to the fixing temperature in the next image area. Sometimes. Therefore, the temperature is controlled so as to keep the fixing belt at the second target temperature lower than the first target temperature corresponding to the image area but higher than the room temperature by a predetermined value, and to the part corresponding to the non-sheet passing area Power is also supplied.

A heating zone H _11, the second thermistor 36 for detecting the temperature of one of the resistance heating elements 56a are installed two. The heating region H _12, the second thermistor 36 for detecting the temperature of one of the resistance heating elements 56a are installed two. That is, a plurality of second thermistors 36 are installed in each heating area that can be simultaneously turned on and off. Then, when the second thermistor 36 detects an abnormal temperature rise of the resistance heating element 156a, the heating control means 42 controls the temperature of the heating area. Therefore, even when the resistance heating element 56a detected by the second thermistor 36 is damaged, the abnormal temperature rise by the other resistance heating element 56a can be detected. In the present embodiment, two second thermistors 36 are installed in each of the heating areas that can be simultaneously turned on and off, but three or more second thermistors may be installed.

  Subsequently, an image forming apparatus according to a second embodiment of the present invention will be described. The same reference numerals as in the image forming apparatus according to the first embodiment denote the same or corresponding parts, and a detailed description thereof will be omitted. Different parts will be described in detail with reference to the drawings.

  The second embodiment is different from the first embodiment in that the configuration of the heater member is different. The details will be described below.

As shown in FIG. 6, the heater member 156 according to the present embodiment has a plurality of resistance heating elements 156a in the longitudinal direction, that is, in the direction orthogonal to the sheet conveyance direction. Opposite electrodes are connected to the upstream and downstream sides of the plurality of resistance heating elements 156a in the sheet conveyance direction, and heat is generated uniformly in the longitudinal direction. The common wiring Wcom and the individual wirings W1 and W2 are connected to the counter electrode to form three heating regions H ₂₁ , H ₂₂ and H ₂₃ . The heating regions H ₂₁ and H ₂₃ are formed at symmetrical positions from the center in the longitudinal direction of the heater member 156, and can be simultaneously turned on / off. That is, the heating regions H ₂₁ and H ₂₃ that can be simultaneously turned ON / OFF are separated and divided, and electrically connected in parallel. The heating areas H ₂₁ and H ₂₃ and the heating area H ₂₂ can be individually and independently heated and controlled by turning on / off the individual wires W 1 and W 2. This makes it possible to reduce the number of switch elements such as triacs and FETs to turn on / off.

In the heating areas H ₂₁ and H ₂₃ , one second thermistor 36 for detecting the temperature of one resistance heating element 156 a is provided. The heating region H _32, the second thermistor 36 for detecting the temperature of one of the resistance heating element 156a is installed two. That is, a plurality of second thermistors 36 are installed in each heating area that can be simultaneously turned on and off. Then, when the second thermistor 36 detects an abnormal temperature rise of the resistance heating element 156a, the heating control means 42 controls the temperature of the heating area. Therefore, even when the resistance heating element 156a detected by the second thermistor 36 is damaged, the abnormal temperature rise by the other resistance heating element 156a can be detected. By electrically connecting heating regions H ₂₁ and H ₂₃ simultaneously heating in parallel, the voltage applied to each second thermistor 36 is prevented from fluctuating at the time of breakage of the second thermistor 36, thereby providing a safer configuration. can do. In the present embodiment, two second thermistors 36 are provided in each heating area that can be simultaneously turned on / off, but three or more second thermistors 36 may be provided.

  Subsequently, an image forming apparatus according to a third embodiment of the present invention will be described. The same reference numerals as in the image forming apparatus according to the first embodiment denote the same or corresponding parts, and a detailed description thereof will be omitted. Different parts will be described in detail with reference to the drawings.

  The third embodiment is different from the first embodiment in that the configuration of the heater member is different. The details will be described below.

As shown in FIG. 7, the heater member 256 of this embodiment has a long resistance heating element 256a in the longitudinal direction, that is, in the direction orthogonal to the sheet conveyance direction. The common wiring Wcom and the individual wirings W1, W2 are connected to the resistance heating element 256a. The common wire Wcom constituting the first conducting electrode and the individual wires W1 and W2 constituting the second conducting electrode form a comb-like conductive portion with respect to the resistance heating element 256a, and a plurality of heating portions Form Then, the resistance heating body 256a has three heating regions _{H 31, H 32, H 33} . The heating regions H ₃₁ and H ₃₃ are formed at symmetrical positions from the center in the longitudinal direction of the heater member 256, and can be simultaneously turned ON / OFF. That is, the heating regions H ₃₁ and H _{33 which} can be simultaneously turned ON / OFF are separately disposed, separated, and electrically connected in parallel. The heating areas H ₃₁ and H ₃₃ and the heating area H ₃₂ can be individually and independently heated and controlled by turning on / off the individual wires W 1 and W 2. This makes it possible to reduce the number of switch elements such as triacs and FETs to turn on / off.

In the heating areas H ₃₁ and H ₃₃ , one second thermistor 36 is provided for detecting the temperature of a part of the heat generating portion of the resistance heating element 256 a. The heating region H _32, the second thermistor 36 for detecting the temperature of a portion of the heat generating portion of the resistance heating element 256a is installed two. That is, a plurality of second thermistors 36 are installed in each heating area that can be simultaneously turned on and off. Then, when the second thermistor 36 detects an abnormal temperature rise of the resistance heating element 256a, the heating control means 42 controls the temperature of the heating area. Therefore, even when a part of the resistance heating element 256a detected by the second thermistor 36 is broken, the abnormal temperature rise by the other part of the resistance heating element 56a can be detected. By electrically connecting heating regions H ₃₁ and H ₃₃ which are simultaneously heated in parallel, it is possible to prevent the fluctuation of the voltage applied to each second thermistor 36 at the time of breakage of the second thermistor 36, thereby providing a safer configuration. can do. In the present embodiment, two second thermistors 36 are provided in each heating area that can be simultaneously turned on / off, but three or more second thermistors 36 may be provided.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this.
In the above-mentioned embodiment, although two or three heating areas are formed, it is not limited to this mode and can set up more heating areas, such as nine. Moreover, as shown in FIG. 8, it is applicable also to the structure which the heating area | region is not divided | segmented.

  In addition, at least one of the plurality of second thermistors disposed in the heating area to be simultaneously heated performs temperature control in a soft manner based on the detected temperature information, and detects high temperature in hardware. Also good. As a result, when an abnormal temperature rise occurs, an abnormality can be detected even in a lower temperature state, so that the safety can be improved.

28 Fixing Belt (Example of Belt-like Fixing Member)
30 Pressure roller (example of pressing member)
36 Second thermistor (temperature detection means)
56 Heater member (an example of a heating member)
56a Resistance heating element (example of heating element)
56b Base material SN fixing nip

Claims (6)

A belt-shaped fixing member that rotates in contact with the unfixed image;
A pressing member that forms a fixing nip portion with the belt-shaped fixing member;
A fixing device configured to fix a sheet-like recording material carrying an unfixed image on a heating member for heating the belt-like fixing member at the fixing nip portion,
The heating member includes a long base material extending in the longitudinal direction of the belt-like fixing member, and a plurality of heating elements formed on the base material.
The plurality of heating elements form at least one heating area which can be ON / OFF controlled at the same time,
In each heating area , the plurality of heating elements are electrically connected in parallel, and a plurality of temperature detection means capable of detecting the temperature of any one of the plurality of heating elements are provided. Fixing device.   2. The fixing device according to claim 1, wherein the at least one heating area is divided and disposed apart in the longitudinal direction of the belt-shaped fixing member, and electrically connected in parallel.   The fixing device according to claim 2, wherein the heating areas divided and disposed are arranged at symmetrical positions with respect to a longitudinal center of the heating member.   4. The fixing device according to claim 2, wherein each divided portion of the heating area has at least one temperature detection unit capable of detecting the temperature of the heating element.   5. At least one of the said temperature detection means performs temperature control by software based on the detected temperature information, While performing high temperature detection in hardware, It is characterized by the above-mentioned. Fixing device.   An image forming apparatus comprising the fixing device according to any one of claims 1 to 5.

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